Microcontroller ATmega1280Operating Voltage 5VInput Voltage (recommended) 7-12VInput Voltage (limits) 6-20VDigital I/O Pins 54 (of which 15 provide PWM output)Analog Input Pins 16DC Current per I/O Pin 40 mADC Current for 3.3V Pin 50 mAFlash Memory 128 KB of which 4 KB used by bootloaderSRAM 8 KBEEPROM 4 KBClock Speed 16 MHz
5v seems a bit high, but that maybe correct, im not sure. I used some while LEDs from cheapo flashlights, and they were running at 4.5v (3 AAA batteries).
I bought 5mm leds without specifications. based on some information found on the internet, a white led uses 5v, 32a.
I believe Vf for White LEDs is generally in the 3.2V to 3.6V range, similar to a Blue LED.